The present invention relates to a defrosting control apparatus for a temperature control system, such as an air-conditioner or heat pump.
Hitherto, as disclosed in JP-B 59-34255, the frosting state of an outdoor heat exchanger has been detected on the basis of both a change in temperature of an indoor heat exchanger and a change in room temperature, and the heating and defrosting operations have been controlled in accordance with the frosting state detected.
However, such a conventional arrangement has the problems that a plurality of temperature sensors are necessary and the circuit obviously becomes complicated. Further, in the temperature control system, since generally the amount of air blown on the indoor side is arbitrarily and variably set, the addition of a wind amount correcting means to the conventional technique causes the circuit to be further complicated. Moreover, in such a conventional arrangement, the temperature of the gas-liquid mixture refrigerant flowing in the heat exchanger is detected. Therefore, the change in the temperatures in the frosting and non-frosting conditions is small and the frosting state must be discriminated within a very narrow temperature range, and this causes the problem such that the detection accuracy is unstable.
In recent years, in many cases, complicated signal processing is performed by a microcomputer as part of a control apparatus. However, the use of many input signal sources (temperature sensors) as in the conventional technique becomes an obstacle in making the program, and there is also a limit in how far the program can be simplified. In addition, the rotational speed of the compressor varies depending on the difference in frequency of the power source, namely, in the cases of 50 Hz and 60 Hz, causing a difference in capability of the refrigerating cycle. Therefore, the temperature of the indoor heat exchanger changes. For example, the rotational speed of the compressor at 60 Hz is higher than that at 50 Hz and the capability of the refrigerating cycle is also larger than that at 50 Hz. Therefore, in general, the temperature of the indoor heat exchanger increases, so that there is the problem that the defrosting operation may not be started although it is necessary to perform the defrosting operation on the outdoor heat exchanger.
The conventional technique has many problems as mentioned above, and further improvement is required.